Diffusion-tensor MRI (DT-MRI) images can be used to obtain information about the microstructure of tissues. The differences in the water diffusion properties of gray matter and white matter in the brain demonstrate a unique source of image contrast, which also has an orientation component corresponding to the direction of axon tracts in white matter anatomy. In this project, novel DT-MRI acquisition techniques will be developed and evaluated for their capacity to decrease noise sensitivity, improve spatial resolution, and minimize image distortion. The diffusion tensor magnitude, shape and orientation of normal brain tissues will be estimated from DT-MRI measurements taken from a set of volunteer studies. These estimates of the tensor properties for normal brain tissues will be used to design a white matter segmentation algorithm. The segmentation algorithm will then be applied to the study of a group of patients with brain tumors. Intraoperative mapping of the cortex and deep white matter will be used to estimate the accuracy of the segmentation. The directional information of the diffusion tensor will also be used in the development of algorithms that will be used to estimate the likely paths of axon fiber bundles. The influences of measurement noise and partial volume effects on axon tracking accuracy and precision will be examined. DT-MRI white matter segmentation will be combined with fMRI images of cortical activation to provide maps of the functional anatomy. Images of the functional anatomy will be created from studies of patients with primary intracranial tumors and the relationship of the tumor location to the functional anatomy will be correlated with the neurological symptoms. Finally, the limitations of the diffusion tensor model accuracy, as a function of mixed tissue components and crossing axons in a single voxel, will be investigated. A new model of tissue diffusion with two tensor components will be evaluated. This project is a comprehensive approach to improving the accuracy and understanding of white matter mapping techniques within in the human brain.